Rail damper

ABSTRACT

A damper ( 18 ) for a rail ( 10 ), includes a deformable material ( 20 ) and an elongate resonant member ( 20, 24 ), the resonant member being of a stiff material as compared to the deformable material and being sized to exhibit a resonant frequency in the range of vibration frequencies of the rail, wherein the resonant member includes a clip ( 26 ) extending therefrom so as to retain the resonant member and the deformable material in place on the rail. The clip preferably extends laterally of the resonant member to grip the underside of the rail. The clip can have an engagement formation on the end thereof, to engage with a like formation of a further damper located on the opposing side of the rail.

FIELD OF THE INVENTION

The present invention relates to a rail damper.

BACKGROUND ART

The noise emitted by moving rail vehicles is a major limitation on theiruse, in that it will limit the ability of operators to install new linesin populated areas, and will limit speeds and traffic volumes onexisting lines. The noise tends to be dominated by rolling noise fromthe wheel/rail interface, which is caused partly by vibration of thewheels and partly by vibration of the track.

It is not possible to select alternative materials, etc, for theseelements since they are subject to very high transient loads during use,and must withstand these. Materials that would be able to absorbvibration and hence reduce noise would be unable to survive in use forany appreciable time. Resilient rail fastenings have been employed toreduce track forces and thereby reduce component damage andstructure-borne noise. However, they have an adverse effect on tracknoise, as they tend to reduce the attenuation of rail vibration.

EP628,660 A1 discloses a rail bar in which a body of high specific massis arranged within a mouldable material of low specific mass.

Our previous application WO99/15732 discloses a rail damper adapted toabsorb a wide range of resonant frequencies in the rail through the useof a damper with resonant members tuned to two frequencies in thespectrum of noise to be absorbed.

SUMMARY OF THE INVENTION

The present invention seeks to provide a means for reducing the tracknoise emitted by a rail system, along the lines of the systems shown inEP628,660 A1 and WO99/15732 but which are more straightforward toinstall.

We therefore provide a damper for a rail, comprising a deformablematerial and an elongate resonant member, the resonant member being of astiff material as compared to the deformable material and being sized toexhibit a resonant frequency in the range of vibration frequencies ofthe rail, wherein the resonant member includes a clip extendingtherefrom so as to retain the resonant member and the deformablematerial in place on the rail.

The clip allows the damper to be fitted to the rail in an extremelyshort time as compared to gluing and curing processes, and with greaterconfidence and less inventory as compared to clamping processes.

The relationship between the resonant member and the deformable materialis not crucial to this invention. If desired, the resonant member can beembedded in the deformable material, either by being enclosed or with asurface exposed, or the deformable material can simply be sandwichedbetween the resonant member and the rail.

The resonant member is elongate and will usually extend alongside therail. The clip then preferably extends laterally of the resonant member,meaning that it can grip the rail, preferably the underside thereof. Theclip can have an engagement formation on the end thereof, to engage witha pre-formed engagement means or with a like formation of a furtherdamper located on the opposing side of the rail. In this latter case, itis preferred that the engagement formation is symmetrical such that bothclips are identical.

A further resonant member can be included, for example as taught inWO99/15732 (or otherwise). The further resonant member is thuspreferably sized to exhibit a different resonant frequency in the rangeof vibration frequencies of the rail. To this end, it can have adifferent profile to the first resonant member. It can be embeddedwithin the deformable material in the same manner as the first.

The deformable material is preferably in an elongate form and/orcontinuous. A deformable material that consisted simply of isolatedislands supporting the resonant member might be less robust and may haveinappropriate elastic properties for transmission of vibration, althoughthese issues may be resolvable through materials selection.

The deformable member can be visco-elastic and/or rubber or rubber-like.It is preferably substantially uniform in composition.

The present invention also provides a rail, to which is attached adamper as defined above. In such a rail, the damper is preferablypositioned on the rail so as to cover the junction between the web andthe foot of the rail. This will be assisted if at least one (or the)resonant member is an elongate angled section, ideally with an anglethat matches the angle between external surfaces of the rail head andfoot.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample, with reference to the accompanying figures in which;

FIG. 1 shows a known rail damper held in place with a clamp;

FIG. 2 shows the damper of the present invention in section, in theprocess of assembly;

FIG. 3 shows a perspective view of the damper of the present invention,in place;

FIG. 4 shows a section of an alternative damper, in place;

FIG. 5 shows a perspective view of a damper according to the presentinvention; and

FIGS. 6 a and 6 b show interlocking parts of clips of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, a known rail and damper are shown, in which therail 10 consists of a wide foot 12, a web 14 and an enlarged head 16. Oneach side of the foot/web join there is a damper 18 constructed inaccordance with WO99/15732. This comprises a body 20 of deformablematerial in which are embedded two elongate bars 22, 24 of a differentsectional profile. These bars 22, 24 resonate at different frequencieswithin the range of vibration frequencies of the rail and the combinedbody 20 and bars 22, 24 forming the damper 18 absorb a wide range ofvibration frequencies from the rail and thereby alleviate noiseemissions.

It can however be difficult to attach the damper 18 to the rail 10. Oneoption is to glue the damper in place or to cure the deformable materialin place on the rail. This approach gives a good attachment but takessome time to install. Another option also shown in FIG. 1 is to use aC-clamp 26, which urges the damper down onto the rail by compressing itin place. This clamp fixes onto the top surface of the damper 18 and theunderside of the rail foot 12. However, this is less secure and requiresa wider range of parts to be stocked.

FIG. 2 shows an alternative design. The rail 10 is loosely fitted with adamper 50 comprising a block of deformable material 52 in which isembedded a resonant member 54 in the form of an elongate steel rod. Asecond resonant member 56 is provided, in the form of a further elongaterod of a different sectional profile. This has on one side a strip 58 ofdeformable material and, extending from the opposing side, one orpreferably a plurality of clips 60. In this case, the clips are of agenerally C-shaped profile and extend from the rod 56 at intervals.Alternatively, the clips could be continuous along the length of theresonant member. They are sized such that when the rod 56 rests on theupper face of the block 52, the distal end of the C-clip 60 pressesagainst the underside of the rail foot. In this way, once the rod 56 isin place, a two-resonator damper is formed which is already held inplace by the clip or clips 60.

As shown in FIG. 2, the first resonator 54 is embedded in the deformablematerial 52 with only one face of the resonator being exposed. This ison the outer face of the deformable material 52 and thus there is alayer of deformable material between the first resonator 54 and the rail10 and on the upper surface of the damper 50. The layer on the uppersurface thus lies between the first resonator 54 and the secondresonator 56 when the latter is in place.

Alternative arrangements are of course possible. For example, anextended layer of deformable material 58 could cover the underside ofthe second resonator 56, instead of or in addition to the layer ofdeformable material on the upper surface of the first resonator 54.

FIG. 3 shows a section of the elongate resonators 54, 56 and the twoclips 60 which extend from the outer face of the second resonator 56 andshow a C-shaped configuration with the lower edge of the C extendingbeneath the rail foot 12. As shown in FIG. 3, the clips have a profilewhich includes an outwardly extending part 62 to provide the necessaryclearance of the rail foot 12, a downwardly extending part 64 to coverthe distance between the second resonator 56 and the attachment point,in this case the lower face of the rail foot 12, and an inwardlyextending part 66 to engage with the attachment point being theunderside of the rail foot 12.

FIG. 3 also shows the deformable material 58 attached to the secondresonator, with a part 68 extending over the upper surface of the secondresonator 56. This part of the deformable material is not expected toplay a major part In the vibration absorption properties of the damperbut may offer an decorative effect and provide a measure ofenvironmental protection.

FIG. 4 shows a three-mass system 100 secured in place on one side of therail 10. First and second resonant members 102 and 104 are embedded in adeformable material 106. A third resonant member 108 lies over thedeformable material a06 and has one or more clamps 110 which extendbeneath the rail foot 12. These clamps resiliently urge the thirdresonant member 108 towards the rail foot 12 and thus trap the first andsecond resonant members 102, 104 to hold the damper 100 in place on therail. A small clearance is provided between one end of the thirdresonant member 108 and the rail 10 to allow the former to vibrate. Thiscould of course be replaced by a layer of deformable material, but amanufacture step is avoided by using a clearance instead. Vibrationswill still be transmitted to the third resonator 108 via the deformablematerial 106 in which the first and second resonators 102, 104 areembedded.

The three resonators 102, 104, 108 are all of a differentcross-sectional profile and all thus generate a system with multipleresonant frequencies. In practice, some resonators could be matched, ifdesired, or if only a single or double frequency damper was required.

In FIG. 4, a standard single-mass damper 112 is provided on the secondside of the rail. The frequency damped by this damper could be the sameas one of those damped by the three-mass damper 100 or it could be afourth frequency. This could of course be replaced with a single-, two-or three-mass damper as set out herein.

FIG. 5 shows a damper 120 comprising a resonator 122 embedded in adeformable material 124 and with (in this case) two clamps 126 extendingfrom the resonator 122 to clamp the latter in place. The dimensions ofthe clamps can again be adjusted to suit the particular arrangement. Afurther block of deformable material (not shown) can be interposedbeneath the resonator 122 to be clamped in place. This block can containfurther resonators tuned to the same or to further frequencies. If thereis no further block of deformable material then a layer of deformablematerial beneath the resonator 122 may be useful.

FIGS. 6 a and 6 b show a modified form of the clamp, applicable to anyof the various dampers described above. The tip 128 of the clamp (seeFIG. 5) will normally lie beneath the rail foot. Where a clamped damperis fitted on either side of the rail, there will be two such tips facingeach other. As shown in FIG. 6 a, these tips can be formed withengagement formations 130 a, 130 b that are adapted to lock together. InFIGS. 6 a and 6 b, the clamps shown from above, are symmetrical and thusthe two parts are identical to evident advantage. A wide range ofengagement formations are suitable, including the half-dovetail camprofiles of FIGS. 6 a and 6 b.

The materials used for the above-described parts can be any suitablematerial exhibiting appropriate properties. A rubber or rubber-likematerial is preferred for the deformable material as this exhibitsappropriate visco-elastic properties. The remaining parts are suitablyof a ferrous material such as steel, although parts of the clip such asthe downwardly extending part 64 could be of a less stiff material suchas nylon or a composite such as a plastics/steel composite.

The damper according to the present invention has a number ofadvantages. In particular;

-   -   the clamping arrangement substitutes for gluing and thereby        reduces installation time    -   the tuned dampers can have 2 or more masses, as desired    -   the dampers can be removed when the life of the rail is expired    -   the dampers can be removed for rail maintenance    -   the dampers can be wider than known designs, to sit between the        sleepers    -   the dampers can be higher than the existing design, since they        could be removed for tamping operations, although clearance for        other equipment such as the worn rail/worn wheel condition will        still have to be taken into account

It will of course be understood that many variations may be made to theabove-described embodiment without departing from the scope of thepresent invention.

1. A damper for a rail comprising a deformable material and an elongateresonant member, the resonant member being of a stiff material ascompared to the deformable material and being sized to exhibit aresonant frequency in the range of vibration frequencies of the rail;wherein the resonant member includes a clip extending therefrom so as toretain the resonant member and the deformable material in place on therail.
 2. A damper according to claim 1 in which the resonant member isembedded in the deformable material.
 3. A damper according to claim 2 inwhich the resonant member is enclosed within the deformable material. 4.A damper according to claim 2 in which a surface of the resonant memberis exposed.
 5. A damper according to claim 1 in which the clip extendslaterally of the resonant member.
 6. A damper according to claim 1 inwhich the clip is adapted to retain the resonant member and thedeformable material in place on the rail by engagement with an undersideof the rail.
 7. A damper according to claim 1 in which the clip has anengagement formation on the end thereof.
 8. A damper according to claim7, adapted to locate on one side of the rail, in which the engagementformation is adapted to engage with a like formation of a further damperlocated on the opposing side of the rail.
 9. A damper according to claim8 in which the engagement formation is symmetrical such that both clipsare identical.
 10. A damper according to claim 1 including a furtherresonant member.
 11. A damper according to claim 10 in which the furtherresonant member is sized to exhibit a different resonant frequency inthe range of vibration frequencies of the rail.
 12. A damper accordingto claim 10 in which the further resonant member has a different profileto the first resonant member.
 13. A damper according to claim 10 inwhich the resonant member is embedded in the deformable material.
 14. Adamper according to claim 13 in which the resonant member is enclosedwithin the deformable material.
 15. A damper according to claim 13 inwhich a surface of the resonant member is exposed.
 16. A damperaccording to claim 1 in which the deformable material is in an elongateform.
 17. A damper according to claim 16 in which the deformablematerial is continuous.
 18. A damper according to claim 1 wherein thedeformable member is visco-elastic.
 19. A damper according to claim 1wherein the deformable member is rubber or rubber-like.
 20. A damperaccording to claim 1 wherein the deformable material is substantiallyuniform in composition.
 21. A rail to which is attached a damperaccording to claim
 1. 22. A rail according to claim 21, the damper beingpositioned on the rail so as to cover the junction between a web and afoot of the rail.
 23. A rail according to claim 21 in which at least oneresonant member is an elongate angled section.
 24. A rail according toclaim 23 in which the angle matches the angle between external surfacesof the head and foot.
 25. (canceled)